delta_common.c revision 312517 
1///////////////////////////////////////////////////////////////////////////////
2//
3/// \file       delta_common.c
4/// \brief      Common stuff for Delta encoder and decoder
5//
6//  Author:     Lasse Collin
7//
8//  This file has been put into the public domain.
9//  You can do whatever you want with this file.
10//
11///////////////////////////////////////////////////////////////////////////////
12
13#include "delta_common.h"
14#include "delta_private.h"
15
16
17static void
18delta_coder_end(void *coder_ptr, const lzma_allocator *allocator)
19{
20	lzma_delta_coder *coder = coder_ptr;
21	lzma_next_end(&coder->next, allocator);
22	lzma_free(coder, allocator);
23	return;
24}
25
26
27extern lzma_ret
28lzma_delta_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
29		const lzma_filter_info *filters)
30{
31	// Allocate memory for the decoder if needed.
32	lzma_delta_coder *coder = next->coder;
33	if (coder == NULL) {
34		coder = lzma_alloc(sizeof(lzma_delta_coder), allocator);
35		if (coder == NULL)
36			return LZMA_MEM_ERROR;
37
38		next->coder = coder;
39
40		// End function is the same for encoder and decoder.
41		next->end = &delta_coder_end;
42		coder->next = LZMA_NEXT_CODER_INIT;
43	}
44
45	// Validate the options.
46	if (lzma_delta_coder_memusage(filters[0].options) == UINT64_MAX)
47		return LZMA_OPTIONS_ERROR;
48
49	// Set the delta distance.
50	const lzma_options_delta *opt = filters[0].options;
51	coder->distance = opt->dist;
52
53	// Initialize the rest of the variables.
54	coder->pos = 0;
55	memzero(coder->history, LZMA_DELTA_DIST_MAX);
56
57	// Initialize the next decoder in the chain, if any.
58	return lzma_next_filter_init(&coder->next, allocator, filters + 1);
59}
60
61
62extern uint64_t
63lzma_delta_coder_memusage(const void *options)
64{
65	const lzma_options_delta *opt = options;
66
67	if (opt == NULL || opt->type != LZMA_DELTA_TYPE_BYTE
68			|| opt->dist < LZMA_DELTA_DIST_MIN
69			|| opt->dist > LZMA_DELTA_DIST_MAX)
70		return UINT64_MAX;
71
72	return sizeof(lzma_delta_coder);
73}
74